Airworthiness Directives; Pratt & Whitney 4000 Series Turbofan Engines

This amendment adopts a new airworthiness directive (AD), that is applicable to Pratt & Whitney (PW) PW4090, PW4090-3, PW4074D, PW4077D, PW4090D, and PW4098 turbofan engines with 15th stage high pressure compressor (HPC) disks having certain part numbers (P/N's). This amendment requires initial and repetitive borescope inspections of 15th stage HPC disks for cracks in the knife edges, eddy current inspections (ECI's) of blade loading slots if required, and removal of cracked disks. In addition, this amendment requires the removal from service of these P/N disks, at a new lower cyclic life limit. This amendment is prompted by two reports of 15th stage HPC disks with cracks in the outer rim front rail of the blade loading slots, and in the front forward and middle knife edges. The actions specified by this AD are intended to prevent 15th stage HPC disk failures from cracks, which could result in an uncontained engine failure.